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A low-power, multiroom sensor network watches for drips and runs on a coin-cell battery.

By Kate Greene

Earlier this month, as Google was snatching up the smart-thermostat maker Nest for $3.2 billion, a lesser known home sensor company made its own announcement. SNUPI Technologies, a Seattle startup, said it had garnered $7.5 million in funding. That might be pocket change compared to the Nest deal, but it was a significant endorsement just ahead of SNUPI’s first product launch: a low-power wireless sensor network called WallyHome that tracks humidity, water leaks, and temperature throughout a building.

There are already many home monitors on the market; some, such as Lowe’s Iris Home Management System and a water leak and flood sensor from General Electric, are even wirelessly networked. What makes WallyHome novel is its use of a low-power communication scheme that lets sensors send data back to an Internet-connected base station over significant distances and through obstructions like walls and floors while sipping power from a coin-cell battery.

SNUPI cofounder Gabe Cohn believes this long-distance, low-power approach will endear the product to homeowners who want a reliable sensor network that requires little maintenance and can be installed easily. The base station plugs into a wall outlet and an Internet router via an Ethernet cable. Six wireless sensors are placed in leak- or humidity-prone areas, such as behind a toilet, under a dishwasher, or near a sump pump. And each sensor’s battery should power the device for up to 10 years without a replacement, Cohn says.

Most sensor networks rely on wireless protocols like Wi-Fi, ZigBee, or Bluetooth to send a signal to a base station tens of feet away. Some of these networks require devices that boost a wireless signal so it can go around walls or through floors, and they tend to require multiple battery replacements during their lifetimes.

Instead of blasting a wireless signal tens of feet, the WallyHome sensors emit a relatively weak wireless signal. While the signal isn’t powerful enough to reach a base station on its own, it can reach inside walls and resonate with the copper wiring that carries electricity. WallyHome effectively turns these internal power lines into antennas, propagating sensor data to a base station, which is plugged into the same lines. Data is then uploaded to a cloud-based data collection and analysis service, and a person can check the status of a sensor using the Web and a smartphone app. The system sends a text, e-mail, or mobile phone alert if water is detected or temperature and humidity thresholds are exceeded. “You have these wireless sensor nodes you can place anywhere in the house or building because power lines go anywhere,” says Cohn.

The concept of using power lines to augment wireless sensor networks arose from research conducted by Cohn and co-inventors Matt Reynolds and Shwetak Patel, both professors at the University of Washington. In addition to cofounding SNUPI (Sensor Network Utilizing Powerline Infrastructure) in 2012, Patel, who was one of MIT Technology Review’s 35 Innovators Under 35 in 2009, also cofounded Zensi, acquired by Belkin in 2010. Patel was awarded a MacArthur award in 2011.

Elizabeth Mead, an analyst at IHS, a research firm, says that energy management is crucial for home networks. Low-power devices are becoming increasingly important, especially as the number of sensors in home networks proliferate.

Cohn hopes WallyHome’s water-watching network will appeal to people who might have a second home that isn’t regularly occupied, or who have previously experienced water damage, which can cause thousands of dollars of damage.

Over time, the system, which runs sensor data through machine-learning algorithms, will eventually be able to infer trends and anticipate changes in the environment, Cohn says. It could, for instance, notice that leaks from frozen pipes are common in certain areas at certain times of the year and issue warnings to customers.

As smart-home technologies ramp up, there’s interest in ensuring interoperability between devices from various vendors (see “CES 2014: Smart Homes Open Their Doors”). Cohn says the WallyHome cloud and mobile device software will be interoperable with existing smart-home products. He adds that future WallyHome sensors will be able to track air quality, monitoring pollen, smoke, and dust.